Stellar burning stages

The reactions involved in the He-burning stage have been discussed in many places (e.g. [5], NACRE [6]). The main ones are displayed in Fig 4. They develop at temperatures in excess of 108 K, and mainly transform 4He into 12C and leO, with some limited contribution to the abundance of some heavier a-particle nuclei (esp. 20Ne,.), at least in massive enough stars. Of very special and dramatic importance for the theories of stellar evolution and of nucleosynthesis is the famed 12C (a, 7) 160 reaction, which has been the subject of a flurry of experimental investigations, as well as of theoretical efforts (for a review, see [11] see also [12] for a recent re-analysis of the case). In spite of that, uncertainties remain, and preclude certain nuclear astrophysics predictions to be made at a satisfactory level (see e.g. [13]). 

Over the 13.7 billion years since the Big Bang, stars have burned nuclear fuel to maintain pressure support against gravitational contraction. In doing so, they have converted the hydrogen and helium left over from the Universe s earliest moments into the heavier elements that make nearly all of chemistry possible. This paper briefly reviews the evolution of stars, the mainline stages of stellar burning, and the side reactions that make Nature s heaviest elements. 

The Mainline Stages of Stellar Burning and Their Products... 

The first stage of stellar nucleosynthesis, which is still occurring in stars such as our sun, is hydrogen burning. In hydrogen burning, protons are converted to 4He nuclei. Since there are no free neutrons present, the reactions differ from those of Big Bang nucleosynthesis. The first reaction that occurs is... 

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